Solenoid switch having a bridging contact on the solenoid plunger



Nov. 9, 1965 s. M. TERRY 3,217,124

SOLENOID SWITCH HAVING A BRIDGING CONTACT ON THE SOLENOID PLUNGER Filed Jan. 29, 1962 l6 I8 I\\\\\\ uumuh l mu mm" 2 3 ,-la 3 E3 NM Fe 54 FIGS 76 75 a 79 H 54 62 eo lg ea 58 /IO 46 s4 1 5e 1 50 I I la 5 I I 20 mun 72 68 H mm mum E INVENTOR STANLEY M. TERRY ATTORNEYS United States Patent 3,217,124 SOLENOID SWITCH HAVING A BRIDGING CON- TACT ON THE SOLENOID PLUNGER Stanley M. Terry, Longmeadow, Mass., assignor, by mesne assignments, to Elci Products Corporation, Carolina,

P.R., a corporation of Puerto Rico Filed Jan. 29, 1962, Ser. No. 169,272 Claims. (Cl. 200-111) This invention relates to solenoid operated electric switches, and deals more particularly with a solenoid switch especially adapted for high vibration applications.

The switch with which this invention is concerned finds particular utility as a starter switch for controlling an electric starting motor associated with an internal combustion engine. Such starter switches are commonly so mounted relative to the engine as to be subject to engine vibration, and in prior switch constructions the vibration has often caused failure of the switch by fatigue or by fretting of various parts which rub together as a result of the vibration. The switch of this invention is so constructed as to minimize wear and failure due to vibration when used as a starter switch, but it is to be understood that it is not necessarily limited to use as a starter switch and that it may be used in other high vibration applications as well.

The general object of this invention is therefore to provide a solenoid operated electric switch capable of prolonged use under vibrating loads without undue wear or failure of its various parts.

A more particular object of this invention is to provide a solenoid switch having means for guiding the solenoid plunger so that the plunger is prevented from cocking in the solenoid bore as it moves between its actuated and unactuated positions and is similarly prevented from moving in anything other than a straight path of minimum wear upon actuation of the solenoid coil.

Another object of this invention is to provide an improvided means for securing a contact washer to the solenoid plunger, which means eliminates free play between the washer and the plunger, provides electrical insulation between the washer and the plunger, and at the same time allows the washer to partake of a limited amount of resilient movement relative to the plunger to insure good square contact between the washer and other fixed contacts when the solenoid is actuated and to act as a high rate contact spring in conjunction with a small plunger overtravel to maintain low contact resistance.

A further object of this invention is to provide an electric solenoid switch adapted for use as a switch for the starter motor of an internal combustion engine and having improved auxiliary contact means for applying full battery voltage to the ignition coil during operation of the starter, said improved auxiliary contact means being of an economical construction yet particularly resistant to failure due to vibration.

A still further object of this invention is to provide a solenoid switch of the above character which switch eliminates expensive parts found in other similar switches and is otherwise simple and inexpensive to manufacure while being rugged and reliable in operation.

Further objects and advantages of the invention will be apparent from the following description and from the drawing forming a part thereof.

The drawing shows a preferred embodiment of the invention and such embodiment will be described, but it will be understood that various changes may be made from the construction disclosed, and that the drawing and description are not to be construed as defining or limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

Of the drawing:

FIG. 1 is a side elevational view of a solenoid switch embodying the present invention.

FIG. 2 is a top view of the switch shown in FIG. 1.

FIG. 3 is a longitudinal sectional view taken on the line 33 of FIG. 2.

FIG. 4 is a longitudinal sectional view taken on the line 44 of FIG. 2.

FIG. 5 is a top view similar to FIG. 2, but in which view the end cover and plunger assembly have been omitted to show more clearly the construction of other parts of the switch.

FIG. 6 is a fragmentary longitudinal sectional view taken on the line 6-6 of FIG. 5.

FIG. 7 is an enlarged sectional view of the auxiliary spring contact employed in the switch and which view is taken on the line 77 of FIG. 8.

FIG. 8 is an elevational view of the auxiliary spring contact shown in FIG. 7, the view being taken looking toward the left in FIG. 7.

FIG. 9 is a schematic wiring diagram illustrating the use of the switch of FIG. 1 in conjunction with the ignition and starting circuit of an automobile engine or the like.

Turning now to the drawing, FIGS. 1 and 2 show the outward appearance of a solenoid switch It) incorporating the present invention. This switch has a generally conventional appearance and includes a housing 12, an end cover 14, two large terminals 16 and 18, two smaller terminals 26 and 22, and a mounting bracket 24. The housing 12 is preferably made' from a molded plastic, such as a phenolic resin, and as shown in FIGS. 1 and 3 consists of a hollow generally cylindrical body closed at its lower end, the upper end being open and having associated therewith a generally radially outwardly extending flange which receives the end cover 14. The end cover is secured to the housing flange by suitable means such as rivets 26, 26. The mounting bracket 24 may take on various diiferent shapes as required for attaching the switch to various different supporting structures.

\Referring to FIGS. 3 and 4, which show the interior of the switch 10, it will be noted that a solenoid coil 28 is positioned in the lower end of the housing 12. This coil comprises many turns of wire wound on a bobbin 30 preferably made of nylon or equivalent mechanical and electrical insulating material. Provided in the bobbin 30 is a centrally located and axially extending bore 32 having a substantially uniform circular cross section throughout its length. The coil 28 and bobbin 30 therefore together define a solenoid coil means having a central bore. Surrounding the coil and bobbin is a magnetic shield member 34 and interposed between the bottom face of the bobbin 30 and the lower end wall of the housing 12 is a magnetic steel bottom washer 36. This washer and the bracket 24 are held to the housing 12 by means of a nose pin 38, the latter pin having an enlarged diameter head or nose which fits into the lower end of the bobbin bore 32 and a reduced diameter portion extending through registering apertures in the bottom washer 36, the end wall of the housing 12 and the bracket 24. The lower end of the nose pin 38 is staked over against the lower face of the bracket 24 as shown in FIGS. 3 and '4 so that the various parts are held thereby in tightly assembled relationship.

'Adjacent the upper face of the bobbin 30 is a top magnetic steel washer 40 and an insulating bobbin lock 42. Both of these latter two members are centrally apertured and the bobbin 30 on its upper face includes a short axially extending portion or chimney 44 which passes through the apertures so that the solenoid coil bore 32 for its entire length is lined with the material of the bobbin 30, said latter material as mentioned being preferably nylon or an equivalent non-magnetic plastic material.

The two large terminals 16 and 18 extend through the side wall of the housing 12 and each at its inner end is formed to provide fixed electrical contacts 46 and 45, respectively. These fixed contacts 46 and 48 comprise enlarged heads on the ends of the terminals 16 and 13 which heads are machined to provide upwardly facing contact surfaces 50 and 52, respectively, located in approximately the same plane passing transversely through the switch. The outer ends of the terminals 16 and 18 are threaded and the terminals are held to the housing 12 by suitable washers and nuts as shown.

The terminal 20 shown in *FIGS. 4 and has associated therewith an auxiliary cont act member 54 which contact member comprises a length of spring material, such as beryllium copper, bent to the shape shown best in FIGS. 4, 7 and 8. The inner end of the terminal includes an enlarged head 56 and the radially outer end of the cont-act 54 includes, as best shown in FIG. 8, a slot 53 defining two tongues 60, which straddle the shank of the terminal 20 and are clamped between the head 56 and the wall of the housing 12. The outer end of the terminal 20 is threaded and the terminal is held to the housing 12 by means of a suitable washer and nut. The radially inner portion of the contact member 54 is bent at substantially a right angle to the outer portion so that the overall shape of the member 54- is substantially that of an L. The inner end of the inner portion is bent longitudinally to form a transversely extending bead on ridge 62 having a relatively small radius in cross section a shown in FIG. 7. The inner portion is also bent transversely along a larger radius, as shown in FIG. 8, so that the bead or ridge 62 actually has a compound curvature. The bead or ridge 62 faces upwardly and defines a contact surface for cooperation with a contact washer as hereinafter described. From FIG. 4 it will be noted that the contact member 54 is substantially a cantilevered member, being fastened to the housing 12 at one end and extending radially inwardly therefrom without support at its other end. The length of this member, however, and its mass is such that its natural frequency of vibration relative to the housing is very high and it is, in fact, quite a bit higher than the vibratory loads which might be imposed on the switch during use with an internal combustion engine. The contact member 54 therefore does not tend to vibrate relative to the housing 12 during use and the possibility of failure due to fatigue and fretting is therefore accordingly highly reduced, if not entirely eliminated.

The terminal 22 is connected electrically with one end of the coil 28 and is used to control the energization of the coil. As shown best in FIGS. 5 and 6, the terminal 22 includes an enlarged head 64 on its inner end and clamped to the wall of the housing 12 by the head 64 is a metallic connecting element 66 to which is soldered, as at 68, one end 70 of the coil 28. The other end of the coil 28 is soldered or otherwise connected to the metallic bottom washer 36 so that the mounting bracket 24, by means of the electrical connection between the bottom washer 36 and the bracket provided by the nose pin 38, serves as the other terminal for the coil 23.

The switch 1t? also preferably includes a quantity of potting material 72 applied through the top of the solenoid coil assembly. This material is preferably applied after the assembly with the housing 12 of everything that is affixed thereto including the terminals '16, 18, 20 and 22, and the spring contact 54. The potting material may therefore and preferably does enclose or surround at least part of the inner ends of the terminals 16 and 18 and the inner end-of the terminal 22 including the conmeeting member 66. It may also enclose a part of the inner end of the terminal 20, but should not be applied to such a level as to obstruct or interfere with the inwardly extending portion of the member 54. The potting material serves to aid in holding the coil unit in the housing '12 and provides a waterproof seal for the coil. In applying the potting material to the switch care is taken to see that none of the material enters or obstructs the coil bore 32. This may be done by providing a plug or shield device which is insered into the coil bore during the potting operation, and which includes a radially extending shoulder for preventing the deposition of potting material adjacent the bore to provide clearance for a return spring. A corollary advantage of this design is that it permits the assembly of the auxiliary contact spring 54 and its associated terminal 20 with the other parts of the switch before the potting operation thereby making it unnecessary to make special provision to shield this area during the potting operation.

Also included in the switch 10 is a plunger 73 which cooperates with the coil 28 and is reciprocated axially in response to the energization and de-energization of the latter. As shown in FIGS. 3 and 4, the plunger includes a first or lower portion 74 which is received by the upper portion of the coil bore 32. The lower portion of the coil bore receives and is closed by the head of the nose pin 38 which head also serves as a stop for limiting the downward travel of the plunger when the coil is energized and as part of the magnetic circuit. The outer surface of the portion 74- is cylindrical in shape and has a diameter closely conforming to that of the bore so that the bore guides the plunger for straight axial motion. The other end portion of the plunger includes a stem 76 which is or may be of reduced diameter as shown and which is received in a guide bore 78 formed in the end cover 14. Adjacent the lower or inner end of the guide bore is a radial shoulder 79 which engages a similar shoulder 81 on the upper end of the plunger when the solenoid coil is de-energized. The guide bore 78 is arranged coaxial with the coil bore 32 and has a diameter closely conforming to that of the stem 76. It will therefore be seen that the plunger is slidably supported at both of its ends so as to be guided for motion in a straight axial path which path is one of minimum wear between the plunger and the bobbin and between the plunger and the end cover 14. Also, this construction enables the upper shoulder 81 of the plunger to be held firmly against the guide bore shoulder 79 by the return spring, hereinafter described, to prevent both axial and radial vibration when the solenoid is not energized. Furthermore, the fact that the outer end of the plunger is guided or supported by the end cover 14 prevents the plunger from assuming a cocked position relative to the coil bore 32, which cocked condition could cause the plunger to bind relative to the bobbin and prevent the switch from operating and/or cause excessive wear. The end cover 14 may be made from various different materials, but preferably it is made from molded nylon or the equivalent so that friction and fretting between it and the stem 76 is reduced.

Carried by the plunger 73 is a contact member which is adapted to simultaneously contact both the fixed contacts 4-6 and 48 to make electrical connection therebetween when the plunger is in its actuated position and to be out of contact with the same contacts 46 and 48 when the plunger is in its unactuated position. As shown in FIGS. 3 and 4, this contact member 80 comprises a washer, of copper or other electrically conductive material, which is secured to the plunger 73 by means of a grommet 82 made of rubber or other resilient electric insulating material. The grommet 82 includes a circumferential groove 84 in its outer surface which groove receives the inner edge portion of the washer 80. A portion of the grommet 82 is therefore radially interposed between the washer 80 and the plunger 73 so that the washer is electrically insulated from the plunger. Also, the Walls of the circumferential groove 84 engage the opposite sides of the washer to normally hold the same in a given position relative to the plunger, Furthermore, the resilient nature of the grommet material allows the washer 80 to be moved resiliently and to a limited extent relative to the plunger to insure a square mating relationship between the contact washer 80 and the contact surfaces 50 and 52 upon actuation, and the grommet will also act as a high rate contact spring in conjunction with a small amount of plunger overtravel to maintain low contact resistance and compensate for normal washer and contact wear at the mating surfaces. The grommet 82 includes a central aperture which is received on a reduced diameter por tion of the plunger, which latter reduced diameter portion is defined by two radial shoulders 86 and 88 on the plunger and which shoulders engage the opposite end faces of the grommet to thereby prevent the latter from moving axially on the plunger and to cooperate with the grommet to hold the washer 80 resiliently yet firmly and without free play to eliminate relative vibration and wear when the solenoid coil is de-energized.

In FIGS. 3 and 4, the plunger 73 is shown in its unactuated position corresponding to de-energization of the coil 28. In this position the contact washer 80 carried by the plunger is positioned in spaced relationship to the contact surfaces 50 and 52 of the contacts 46 and 48 and also in spaced relationship to the contact surface 62 of the auxiliary contact 54. When the solenoid coil 28 is energized, the plunger 73 is drawn downward from the position shown in FIGS. 3 and 4 until the contact washer 80 rests firmly on the contact surfaces 50 and 52. The position of the plunger at htis time is referred to as its actuated position. One feature of the invenion is that as the plunger '73 reaches its actuated position the resiliency imparted to the contact element 80 by the grommet 82 permits the washer to move slightly angularly relative to the plunger 73 as may be required to allow it to seat itself squarely on the contact surfaces 50 and 52. The same resiliency of the grommet also allows the washer to move a slight distance longitudinally of the plunger so that the grommet acts as a high rate spring in conjunction with a small amount of plunger overtravel to hold the washer and the terminals 46 and 48 firmly in contact for low resistance. When the plunger is in its actuated position the bottom thereof engages the nose pin or stop 58. This reduces the reluctance of the magnetic circuit and allows the plunger to be held in its actuated position by a smaller current than required to move it to such postion.

The plunger 73 is biased toward its unactuated position by means of a coil spring 90 which surrounds the plunger and is disposed between the grommet 82 and the insulating bobbin lock 42. When the coil 28 is energized the plunger '73 is moved to its actuated position against the force of the spring 90 and when the coil is de-energized the spring 90 returns the plunger to its unactuated position.

The location and arrangement of the auxiliary contact 54 is such htat the upwardly facing contact surface 62 thereof is at a level above the plane of the contact surfaces 50 and 52. so that the surface 62 is engaged by the contact washer 80 before the washer 80 is brought into contact with the surfaces 50 and 52. Thus, when the plunger 73 is in its actuated position the auxiliary contact 54 is engaged thereby and displaced a slight distance from its normal position so as to be held against the washer with some spring force. Thus, when the plunger is in its actuated condition, the contact washer 80 serves to make electrical contact between all three contacts 46, 48 and 54.

As mentioned, the switch finds particular utility in connection with the ignition and starting circuit of an internal combustion engine, and therefore for the purpose of describing the operation of the switch, FIG. 9 shows a Wiring diagram of the switch as applied to such a circuit. Referring to FIG. 9, the elements within the broken line ibox represent schematically various elements of the switch 10, while elements located outside the box represent elements of the external circuit to which the switch is applied. In this figure the elements inside the box have been given reference numerals corresponding to corresponding elements of the switch shown in FIGS. 1 to 8, inclusive. Numeral 92 represents a storage battery, numeral 94 a dropping resistor, numeral 96 the primary side of the ignition coil, numeral 98 the breaker points and numeral 102 the starting motor. An ignition switch is shown at 104 and a starting switch is shown at 106.

From this figure it will be understood that when the solenoid coil 28 is energized by closing the starter switch 106 the plunger 73 is drawn downwardly and brings the contact washer into engagement with the fixed contacts 46 and 48. This in turn closes a direct circuit between the battery 92 and the starting motor 102 so that the latter motor is energized. At the same time a closed circuit is also provided between the contact 46 and the auxilitry contact 54 by the washer 80. The terminal 20 is in turn connected to a point between the dropping resistor 94 and the primary ignition coil 96 so that when the connection is made between the terminals 46 and 54 the dropping resistor 94 is shunted out of the ignition circuit and full battery potential is applied to the primary coil 96 in a manner well known in the art. This in turn means that as the starting motor 102 is energized full battery potential is applied to the ignition coil as an aid to starting. When the starting switch 106 is later opened the contact washer 80 returns to its unactuated position which de-energizes the starting motor and opens the circuit between the contact 46 and the auxiliary contact 54. The dropping resistor 94 is therefore brought back into series operation with the ignition coil 96.

The invention claimed is:

1. In a solenoid operated electric switch the combination comprising a housing, a solenoid coil positioned in said housing and having a central axially extending bore, a plunger having one portion thereof slidably received by said coil for axial reciprocating movement between actuated and unactuated positions in response to energization and de-energization of said solenoid coil and another portion extending outwardly from said coil bore, a pair of contacts fixed relative to said housing and disposed in circumaxially spaced relation about the axis of said plunger, said contacts defining two contact surfaces located in a common plane substantially normal to the axis of said plunger, a radially and circumferentially extending contact member carried by said outwardly extending plunger portion which contact member is so positioned on said plunger as to contact said fixed contacts when said plunger is in its actuated position and to be out of contact with said contacts when said plunger is in its unactuated position, and a fourth contact carried by said housing which fourth contact comprises a spring member having an outer end fixed to said housing and which spring member extends radially inwardly in a cantilevered fashion from said outer end and has an inner end normally spaced in the direction toward said contact member from said common plane so as to be engaged by said contact member and displaced a slight distance from its normal position when said contact member engages said two fixed contacts.

2. In a solenoid operated electric switch, the combination comprising a solenoid coil having a central bore, a plunger having a portion thereof slidably received by said coil bore and another portion thereof extending outwardly from said coil bore, two contacts fixed relative to said coil, a contact member carried by said outwardly extending plunger portion and arranged to simultaneously contact bot of said fixed contacts to make an electrical connection therebetween when said plunger is in one axial position relative to said coil and to be out of contact with said fixed contacts when said plunger is in a second axial position relative to said coil, and means for mounting said contact member to and electrically insulating the same from said plunger and for permitting said contact member to partake of resilient movement both angularly and axially relative to said plunger, said contact member including an opening for receiving said plunger with the marginal portion of said contact member surrounding said opening being radially spaced a substantial distance from said plunger, and said mounting means comprising a member made of resilient electrically insulating material radially interposed between said plunger and said contact member and fixed at its radially inner portion to said plunger and at its radially outer portion to said contact member.

3. The combination as defined in claim 2 further characterized by means defining a guide bore fixed relative to said coil for slidably receiving and supporting the free end portion of said outwardly extending portion of said plunger, a helical compression spring surrounding said plunger and located between said coil and said contact member for urging said plunger outwardly relative to said coil, and means defining two shoulders respectively fixed to said plunger and to said coil and coengageable with one another to limit said outward movement of said plunger, the shoulder fixed relative to said plunger being located adjacent said free end portion thereof and the shoulder fixed relative to said coil being located adjacent the end of said guide bore facing said coil.

4. The combination as defined in claim 2 further characterized by said two contacts defining two contact surfaces located in a common plane substantially normal to the axis of said plunger and which contact surfaces are contacted by said contact member when said plunger is in said one axial position, and another contact comprising a spring member having a radially outer end fixed relative to said coil and which spring member extends radially inwardly in a cantilevered fashion from said outer end and has a free inner end normally spaced in the direction toward said contact member from said common plane so as to be engaged by said contact memmer and displaced a slight distance from its normal position when said contact member engages said two fixed contacts.

5. In a solenoid operated electric switch, the combination comprising a solenoid coil having a central bore, a plunger having a portion thereof slidably received by said coil bore and another portion thereof extending outwardly from said coil bore, said outwardly extending portion of said plunger including a reduced diameter portion defining two axially spaced radial shoulders, two contacts fixed relative to said coil, a contact Washer carried by said outwardly extending plunger portion and arranged to simultaneously contact both of said fixed contacts to make an electrical connection therebetween when said plunger is in one axial position relative to said coil and to be out of contact with said fixed contacts when said plunger is in another axial position relative to said coil, said contact washer having a central opening through which said plunger passes with the marginal portion of said contact washer surrounding said opening being radially spaced a substantial distance from said plunger, and a grommet made of resilient electrical insulating material for mounting said contact member to and electrically insulating the same from said plunger and for permitting said contact washer to partake of resilient movement both angularly and axially relative to said plunger, said grommet having a radially inner portion located between said two plunger shoulders so as to be axially fixed to said plunger and further having a radially outer portion with a circumferential groove which receives said contact washer, said groove being of such a size that the walls thereof engage opposite sides of said contact washer.

References Cited by the Examiner UNITED STATES PATENTS 888,340 5/08 Macloskie 200-111 1,817,155 8/31 Leece 200111 1,928,846 10/33 Allen 200-4 11 1,993,070 3/35 Middleton 200--111 2,174,313 9/39 Coffey 2001'l1 2,326,342 8/43 Ehrlich 200-l11 2,391,277 12/45 Stapleton 2001 11 2,447,890 8/ 48 Alvino 200-1 11 2,521,969 9/50 Dugan 200-111 2,688,100 8/54 Wolf 200-111 2,923,864 2/60 Blakistone 200-111 2,933,573 4/60 Strider 200104 BERNARD A. GILHEANY, Primary Examiner.

RICHARD M. WOOD, Examiner. 

2. IN A SOLENOID OPERATED ELECTRIC SWITCH, THE COMBINATION COMPRISING A SOLENOID COIL HAVING A CENTRAL BORE, A PLUNGER HAVING A PORTION THEREOF SLIDABLY RECEIVED BY SAID COIL BORE AND ANOTHER PORTION THEREOF EXTENDING OUTWARDLY FROM SAID COIL BORE, TWO CONTACTS FIXED RELATIVE TO SAID COIL, A CONTACT MEMBER CARRIED BY SAID OUTWARDLY EXTENDING PLUNGER PORTION AND ARRANGED TO SIMULTANEOUSLY CONTACT BOTH OF SAID FIXED CONTACTS TO MAKE AN ELECTRICAL CONNECTION THEREBETWEEN WHEN SAID PLUNGER IS IN ONE AXIAL POSITION RELATIVE TO SAID COIL AND TO BE OUT OF CONTACT WITH SAID FIXED CONTACTS WHEN SAID PLUNGER IS IN A SECOND AXIAL POSITION RELATIVE TO SAID COIL, AND MEANS FOR MOUNTING SAID CONTACT MEMBER TO ANE ELECTRICALLY INSULATING THE SAME FROM SAID PLUNGER AND FOR PERMITTING SAID CONTACT MEMBER TO PARTAKE OF RESILIENT MOVEMENT BOTH ANGULARLY AND AXIALLY RELATIVE TO SAID PLUNGER, SAID CONTACT MEMBER INCLUDING AN OPENING FOR RECEIVING SAID PLUNGER WITH THE MARGINAL PORTION OF SAID CONTACT MEMBER SURROUNDING SAID OPENING BEING RADIALLY SPACED A SUBSTANTIALLY DISTANCE FROM SAID PLUNGER, AND SAID MOUNTING MEANS COMPRISING A MEMBER MADE OF RESILIENT ELECTRICALLY INSULATING MATERIAL RADIALLY IN TERPOSED BETWEEN SAID PLUNGER AND SAID CONTACT MEMBER AND FIXED AT ITS RADIALLY INNER PORTION TO SAID PLUNGER AND AT ITS RADIALLY OUTER PORTION TO SAID CONTACT MEMBER. 